Bernie Ecclestone’s plan to increase the F1 calendar to 21 races or more could be thwarted by the new engine regulations which come into force next year.

Along with the switch to 1.6-litre V6 turbo engines teams will only be able to use five engines per car per season. They are already concerned about the prospect of each engine doing four races and an additional round would mean one engine having to be used in five events.

According to Autosport one manufacturer has already contacted the FIA to warn about the problems posed by extending the calendar beyond 20 races.

There are 19 races on the calendar this year and even though India will be absent from next year’s schedule the number of events vying for a slot on the schedule may still mean it features more than 20 stops.

Austria is likely to have a round at the Red Bull Ring and Russia’s inaugural race in Sochi has been several years in the making.

A draft calendar which appeared over the Italian Grand Prix weekend also indicated a return to Mexico is planned.

The calendar did not include a space for New Jersey’s planned race, which was also on the 2013 schedule before being postponed. They may still have a chance to gain a place on the calendar, but concerns over engine life will make it even harder to achieve.